Single focal length lens system, camera, and automobile

ABSTRACT

A single focal length lens system which, in order from an object side to an image side, includes a first unit, an aperture diaphragm, and a second unit is provided. The second unit includes a cemented lens having positive optical power, and a joint surface of the cemented lens is an aspheric surface. The cemented lens satisfies a condition: |dn/dt1| MAX ≦2.67×10 −5  (|dn/dt1| MAX : a maximum value of absolute values of relative refractive index temperature coefficients in an atmosphere at 0 to 20° C. with respect to light having a wavelength range of 580 to 640 nm, which is calculated for each of lens elements constituting the cemented lens).

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of International Application No.PCT/JP2014/005414, filed on Oct. 27, 2014, which in turn claims thebenefit of Japanese Application No. 2013-233733 filed on Nov. 12, 2013,the disclosures of which Applications are incorporated by referenceherein.

BACKGROUND

1. Field

The present disclosure relates to single focal length lens systems,cameras, and automobiles.

2. Description of the Related Art

Japanese Laid-Open Patent Publication No. 2008-076716 discloses awide-angle lens system having a relatively small number of lenses, i.e.,six lenses as a whole, in which the shape, arrangement, and the like ofeach lens are optimized.

SUMMARY

The present disclosure provides a single focal length lens system whichhas a sufficiently wide angle of view, a small size, and excellenttemperature characteristics. In addition, the present disclosureprovides a camera including the single focal length lens system, and anautomobile including the camera.

A single focal length lens system according to the present disclosure,in order from an object side to an image side, includes: a first unit;an aperture diaphragm; and a second unit, wherein

the first unit includes a lens element made of glass at a positionclosest to the object side,

the second unit includes a cemented lens having positive optical power,and a joint surface of the cemented lens is an aspheric surface, and

the following conditions (1), (2) and (3) are satisfied:

|dn/dt1|_(MAX)≦2.67×10⁻⁵  (1)

2ω_(DIA)≧>150  (2)

2.0≦f _(CEM) /f<4.0  (3)

-   -   where    -   |dn/dt1|_(MAX) is a maximum value of absolute values of relative        refractive index temperature coefficients in an atmosphere at 0        to 20° C. with respect to light having a wavelength range of 580        to 640 nm, which is calculated for each of lens elements        constituting the cemented lens,

2ω_(DIA) is a diagonal angle of view)(°,

f_(CEM) is a focal length at d-line of the cemented lens, and

f is a focal length at d-line of the entire system.

A camera according to the present disclosure includes:

a single focal length lens system; and

an imaging device which captures an image of light converged by thesingle focal length lens system, wherein

the single focal length lens system, in order from an object side to animage side, includes: a first unit; an aperture diaphragm; and a secondunit, wherein

the first unit includes a lens element made of glass at a positionclosest to the object side,

the second unit includes a cemented lens having positive optical power,and a joint surface of the cemented lens is an aspheric surface, and

the following conditions (1), (2) and (3) are satisfied:

|dn/dt1|_(MAX)≦2.67×10⁻⁵  (1)

2ω_(DIA)≧150  (2)

2.0<f _(CEM) /f<4.0  (3)

where

|dn/dt1|_(MAX) is a maximum value of absolute values of relativerefractive index temperature coefficients in an atmosphere at 0 to 20°C. with respect to light having a wavelength range of 580 to 640 nm,which is calculated for each of lens elements constituting the cementedlens,

2ω_(DIA) is a diagonal angle of view)(°),

f_(CEM) is a focal length at d-line of the cemented lens, and

f is a focal length at d-line of the entire system.

An automobile according to the present disclosure includes:

a camera; and

a processing unit which detects external environment on the basis of theimage captured by an t imaging device included in the camera, andcontrols each part, wherein

the camera includes:

a single focal length lens system; and

an imaging device which captures an image of light converged by thesingle focal length lens system, wherein

the single focal length lens system, in order from an object side to animage side, includes: a first unit; an aperture diaphragm; and a secondunit, wherein the first unit includes a lens element made of glass at aposition closest to the object side,

the second unit includes a cemented lens having positive optical power,and a joint surface of the cemented lens is an aspheric surface, and

the following conditions (1), (2) and (3) are satisfied:

|dn/dt1|_(MAX)≦2.67×10⁻⁵  (1)

2ω_(DIA)≧150  (2)

2.0<f _(CEM) /f<4.0  (3)

where

|dn/dt1|mAx is a maximum value of absolute values of relative refractiveindex temperature coefficients in an atmosphere at 0 to 20° C. withrespect to light having a wavelength range of 580 to 640 nm, which iscalculated for each of lens elements constituting the cemented lens,

2ω_(DIA) is a diagonal angle of view)(°),

f_(CEM) is a focal length at d-line of the cemented lens, and

f is a focal length at d-line of the entire system.

The single focal length lens system according to the present disclosurehas a diagonal angle of view significantly widened to about 150° ormore, is small in size, causes less change in optical characteristicseven with temperature change in a range of about 20 to 80° C., and alsohas excellent temperature characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lens arrangement diagram showing an infinity in-focuscondition of a single focal length lens system according to Embodiment 1(Numerical Example 1);

FIG. 2 is a longitudinal aberration diagram of the infinity in-focuscondition of the single focal length lens system according to NumericalExample 1;

FIG. 3 is a lens arrangement diagram showing an infinity in-focuscondition of a single focal length lens system according to Embodiment 2(Numerical Example 2);

FIG. 4 is a longitudinal aberration diagram of the infinity in-focuscondition of the single focal length lens system according to NumericalExample 2;

FIG. 5 is a lens arrangement diagram showing an infinity in-focuscondition of a single focal length lens system according to Embodiment 3(Numerical Example 3);

FIG. 6 is a longitudinal aberration diagram of the infinity in-focuscondition of the single focal length lens system according to NumericalExample 3;

FIG. 7 is a lens arrangement diagram showing an infinity in-focuscondition of a single focal length lens system according to Embodiment 4(Numerical Example 4);

FIG. 8 is a longitudinal aberration diagram of the infinity in-focuscondition of the single focal length lens system according to NumericalExample 4;

FIG. 9 is a lens arrangement diagram showing an infinity in-focuscondition of a single focal length lens system according to Embodiment 5(Numerical Example 5);

FIG. 10 is a longitudinal aberration diagram of the infinity in-focuscondition of the single focal length lens system according to NumericalExample 5;

FIG. 11 is a lens arrangement diagram showing an infinity in-focuscondition of a single focal length lens system according to Embodiment 6(Numerical Example 6);

FIG. 12 is a longitudinal aberration diagram of the infinity in-focuscondition of the single focal length lens system according to NumericalExample 6;

FIG. 13 is a schematic diagram showing an in-vehicle camera includingthe single focal length lens system according to Embodiment 1, and anautomobile having the in-vehicle camera at a position on the rear sidethereof; and

FIG. 14 is a schematic diagram showing: the automobile having thein-vehicle camera at a position on the rear side thereof; points whereit is determined whether visual recognition of the back view of theautomobile on the basis of an image captured by the in-vehicle camera ispossible; and a region including the points.

DETAILED DESCRIPTION

Hereinafter, embodiments will be described in detail with reference tothe drawings as appropriate. However, descriptions more detailed thannecessary may be omitted. For example, detailed description of alreadywell known matters or description of substantially identicalconfigurations may be omitted. This is intended to avoid redundancy inthe description below, and to facilitate understanding of those skilledin the art.

It should be noted that the inventors provide the attached drawings andthe following description so that those skilled in the art can fullyunderstand this disclosure. Therefore, the drawings and description arenot intended to limit the subject defined by the claims.

In the present disclosure, a first unit is a unit composed of at leastone lens element, and a second unit is a unit composed of at least twolens elements. The power, the composite focal length, and the like ofeach unit are determined in accordance with the type, the number, thearrangement, and the like of the lens elements constituting the unit.

Embodiments 1 to 6 Single Focal Length Lens System

FIGS. 1, 3, 5, 7, 9 and 11 are lens arrangement diagrams of single focallength lens systems according to Embodiments 1 to 6, respectively, andeach diagram shows the single focal length lens system in an infinityin-focus condition. In each Fig., an asterisk “*” imparted to aparticular surface indicates that the surface is aspheric. In each Fig.,a straight line located on the most right-hand side indicates theposition of an image surface S. A parallel plate CG is disposed on theobject side of the image surface S

Embodiment 1

As shown in FIG. 1, the single focal length lens system according toEmbodiment 1, in order from the object side to the image side, comprisesa first lens element L1, a second lens element L2, a third lens elementL3, an aperture diaphragm A, and a cemented lens composed of a fourthlens element L4 and a fifth lens element L5. The first lens element L1,the second lens element L2, and the third lens element L3 constitute afirst unit, and the cemented lens constitutes a second unit.

The first lens element L1 is a lens element which has negative opticalpower and is made of glass. The first lens element L1 is a negativemeniscus lens element with the convex surface facing the object side.

The second lens element L2 is a lens element which has negative opticalpower and is made of resin. The second lens element L2 is a bi-concavelens element. In the second lens element L2, the object-side andimage-side concave surfaces are aspheric surfaces. The image-sideconcave surface is an aspheric surface the negative optical power ofwhich decreases with distance from the optical axis.

The third lens element L3 is a lens element which has positive opticalpower and is made of resin. The third lens element L3 is a bi-convexlens element. In the third lens element L3, the object-side andimage-side convex surfaces are aspheric surfaces. The object-side convexsurface is an aspheric surface the positive optical power of whichincreases with distance from the optical axis. The image-side convexsurface is an aspheric surface the positive optical power of whichdecreases with distance from the optical axis.

The cemented lens is obtained by cementing the fourth lens element L4and the fifth lens element L5, and has positive optical power. Thefourth lens element L4 is a lens element which has negative opticalpower and is made of glass. The fourth lens element L4 is a negativemeniscus lens element with the convex surface facing the object side.The fifth lens element L5 is a lens element which has positive opticalpower and is made of glass. The fifth lens element L5 is a bi-convexlens element.

In the cemented lens, the object-side convex surface of the fourth lenselement L4, a joint surface between the fourth lens element L4 and thefifth lens element L5, and the image-side convex surface of the fifthlens element L5 are aspheric surfaces. The object-side convex surface ofthe fourth lens element L4 is an aspheric surface the positive opticalpower of which decreases with distance from the optical axis. The jointsurface between the fourth lens element L4 and the fifth lens element L5is an aspheric surface which is convex toward the object side, and theoptical power of which decreases with distance from the optical axis.The image-side convex surface of the fifth lens element L5 is anaspheric surface the positive optical power of which decreases withdistance from the optical axis.

Embodiment 2

As shown in FIG. 3, the single focal length lens system according toEmbodiment 2, in order from the object side to the image side, comprisesa first lens element L1, a second lens element L2, a third lens elementL3, an aperture diaphragm A, and a cemented lens composed of a fourthlens element L4 and a fifth lens element L5. The first lens element L1,the second lens element L2, and the third lens element L3 constitute afirst unit, and the cemented lens constitutes a second unit.

The first lens element L1 is a lens element which has negative opticalpower and is made of glass. The first lens element L1 is a negativemeniscus lens element with the convex surface facing the object side.

The second lens element L2 is a lens element which has negative opticalpower and is made of glass. The second lens element L2 is a bi-concavelens element.

The third lens element L3 is a lens element which has positive opticalpower and is made of glass. The third lens element L3 is a bi-convexlens element.

The cemented lens is obtained by cementing the fourth lens element L4and the fifth lens element L5, and has positive optical power. Thefourth lens element L4 is a lens element which has positive opticalpower and is made of glass. The fourth lens element L4 is a bi-convexlens element. The fifth lens element L5 is a lens element which hasnegative optical power and is made of glass. The fifth lens element L5is a negative meniscus lens element with the concave surface facing theobject side.

In the cemented lens, the object-side convex surface of the fourth lenselement L4, a joint surface between the fourth lens element L4 and thefifth lens element L5, and the image-side convex surface of the fifthlens element L5 are aspheric surfaces. The object-side convex surface ofthe fourth lens element L4 is an aspheric surface the positive opticalpower of which increases with distance from the optical axis. The jointsurface between the fourth lens element L4 and the fifth lens element L5is an aspheric surface which is convex toward the image side, and theoptical power of which decreases with distance from the optical axis.The image-side convex surface of the fifth lens element L5 is anaspheric surface the positive optical power of which decreases withdistance from the optical axis.

Embodiment 3

As shown in FIG. 5, the single focal length lens system according toEmbodiment 3, in order from the object side to the image side, comprisesa first lens element L1, a second lens element L2, a third lens elementL3, an aperture diaphragm A, and a cemented lens composed of a fourthlens element L4 and a fifth lens element L5. The first lens element L1,the second lens element L2, and the third lens element L3 constitute afirst unit, and the cemented lens constitutes a second unit.

The first lens element L1 is a lens element which has negative opticalpower and is made of glass. The first lens element L1 is a negativemeniscus lens element with the convex surface facing the object side.

The second lens element L2 is a lens element which has negative opticalpower and is made of glass. The second lens element L2 is a negativemeniscus lens element with the convex surface facing the object side.

The third lens element L3 is a lens element which has positive opticalpower and is made of glass. The third lens element L3 is a bi-convexlens element.

The cemented lens is obtained by cementing the fourth lens element L4and the fifth lens element L5, and has positive optical power. Thefourth lens element L4 is a lens element which has negative opticalpower and is made of glass. The fourth lens element L4 is a negativemeniscus lens element with the convex surface facing the object side.The fifth lens element L5 is a lens element which has positive opticalpower and is made of glass. The fifth lens element L5 is a bi-convexlens element.

In the cemented lens, the object-side convex surface of the fourth lenselement L4, a joint surface between the fourth lens element L4 and thefifth lens element L5, and the image-side convex surface of the fifthlens element L5 are aspheric surfaces. The object-side convex surface ofthe fourth lens element L4 is an aspheric surface the positive opticalpower of which decreases with distance from the optical axis. The jointsurface between the fourth lens element L4 and the fifth lens element L5is an aspheric surface which is convex toward the object side, and theoptical power of which decreases with distance from the optical axis.The image-side convex surface of the fifth lens element L5 is anaspheric surface the positive optical power of which decreases withdistance from the optical axis.

Embodiment 4

As shown in FIG. 7, the single focal length lens system according toEmbodiment 4, in order from the object side to the image side, comprisesa first lens element L1, a second lens element L2, a third lens elementL3, an aperture diaphragm A, and a cemented lens composed of a fourthlens element L4 and a fifth lens element L5. The first lens element L1,the second lens element L2, and the third lens element L3 constitute afirst unit, and the cemented lens constitutes a second unit.

The first lens element L1 is a lens element which has negative opticalpower and is made of glass. The first lens element L1 is a negativemeniscus lens element with the convex surface facing the object side.

The second lens element L2 is a lens element which has negative opticalpower and is made of resin. The second lens element L2 is a bi-concavelens element. In the second lens element L2, the object-side andimage-side concave surfaces are aspheric surfaces. The object-sideconcave surface is an aspheric surface the negative optical power ofwhich decreases with distance from the optical axis. The image-sideconcave surface is an aspheric surface the negative optical power ofwhich decreases with distance from the optical axis.

The third lens element L3 is a lens element which has positive opticalpower and is made of resin. The third lens element L3 is a bi-convexlens element. In the third lens element L3, the object-side andimage-side convex surfaces are aspheric surfaces. The object-side convexsurface is an aspheric surface the positive optical power of whichdecreases with distance from the optical axis.

The cemented lens is obtained by cementing the fourth lens element L4and the fifth lens element L5, and has positive optical power. Thefourth lens element L4 is a lens element which has negative opticalpower and is made of glass. The fourth lens element L4 is a negativemeniscus lens element with the convex surface facing the object side.The fifth lens element L5 is a lens element which has positive opticalpower and is made of glass. The fifth lens element L5 is a bi-convexlens element.

In the cemented lens, the object-side convex surface of the fourth lenselement L4, a joint surface between the fourth lens element L4 and thefifth lens element L5, and the image-side convex surface of the fifthlens element L5 are aspheric surfaces. The object-side convex surface ofthe fourth lens element L4 is an aspheric surface the positive opticalpower of which decreases with distance from the optical axis. The jointsurface between the fourth lens element L4 and the fifth lens element L5is an aspheric surface which is convex toward the object side, and theoptical power of which decreases with distance from the optical axis.The image-side convex surface of the fifth lens element L5 is anaspheric surface the positive optical power of which decreases withdistance from the optical axis.

Embodiment 5

As shown in FIG. 9, the single focal length lens system according toEmbodiment 5, in order from the object side to the image side, comprisesa first lens element L1, a second lens element L2, a third lens elementL3, an aperture diaphragm A, and a cemented lens composed of a fourthlens element L4 and a fifth lens element L5. The first lens element L1,the second lens element L2, and the third lens element L3 constitute afirst unit, and the cemented lens constitutes a second unit.

The first lens element L1 is a lens element which has negative opticalpower and is made of glass. The first lens element L1 is a negativemeniscus lens element with the convex surface facing the object side.

The second lens element L2 is a lens element which has negative opticalpower and is made of resin. The second lens element L2 is a bi-concavelens element. In the second lens element L2, the object-side andimage-side concave surfaces are aspheric surfaces. The object-sideconcave surface is an aspheric surface the negative optical power ofwhich decreases with distance from the optical axis. The image-sideconcave surface is an aspheric surface the negative optical power ofwhich decreases with distance from the optical axis.

The third lens element L3 is a lens element which has positive opticalpower and is made of resin. The third lens element L3 is a bi-convexlens element. In the third lens element L3, the object-side andimage-side convex surfaces are aspheric surfaces. The object-side convexsurface is an aspheric surface the positive optical power of whichdecreases with distance from the optical axis.

The cemented lens is obtained by cementing the fourth lens element L4and the fifth lens element L5, and has positive optical power. Thefourth lens element L4 is a lens element which has negative opticalpower and is made of glass. The fourth lens element L4 is a negativemeniscus lens element with the convex surface facing the object side.The fifth lens element L5 is a lens element which has positive opticalpower and is made of glass. The fifth lens element L5 is a bi-convexlens element.

In the cemented lens, the object-side convex surface of the fourth lenselement L4, a joint surface between the fourth lens element L4 and thefifth lens element L5, and the image-side convex surface of the fifthlens element L5 are aspheric surfaces. The joint surface between thefourth lens element L4 and the fifth lens element L5 is an asphericsurface which is convex toward the object side, and the optical power ofwhich decreases with distance from the optical axis. The image-sideconvex surface of the fifth lens element L5 is an aspheric surface thepositive optical power of which decreases with distance from the opticalaxis.

Embodiment 6

As shown in FIG. 11, the single focal length lens system according toEmbodiment 6, in order from the object side to the image side, comprisesa first lens element L1, a second lens element L2, a third lens elementL3, an aperture diaphragm A, and a cemented lens composed of a fourthlens element L4 and a fifth lens element L5. The first lens element L1,the second lens element L2, and the third lens element L3 constitute afirst unit, and the cemented lens constitutes a second unit.

The first lens element L1 is a lens element which has negative opticalpower and is made of glass. The first lens element L1 is a negativemeniscus lens element with the convex surface facing the object side.

The second lens element L2 is a lens element which has negative opticalpower and is made of glass. The second lens element L2 is a bi-concavelens element.

The third lens element L3 is a lens element which has positive opticalpower and is made of glass. The third lens element L3 is a bi-convexlens element.

The cemented lens is obtained by cementing the fourth lens element L4and the fifth lens element L5, and has positive optical power. Thefourth lens element L4 is a lens element which has positive opticalpower and is made of glass. The fourth lens element L4 is a bi-convexlens element. The fifth lens element L5 is a lens element which hasnegative optical power and is made of glass. The fifth lens element L5is a negative meniscus lens element with the concave surface facing theobject side.

In the cemented lens, the object-side convex surface of the fourth lenselement L4, a joint surface between the fourth lens element L4 and thefifth lens element L5, and the image-side convex surface of the fifthlens element L5 are aspheric surfaces. The object-side convex surface ofthe fourth lens element L4 is an aspheric surface the positive opticalpower of which increases with distance from the optical axis. The jointsurface between the fourth lens element L4 and the fifth lens element L5is an aspheric surface which is convex toward the image side, and theoptical power of which decreases with distance from the optical axis.The image-side convex surface of the fifth lens element L5 is anaspheric surface the positive optical power of which decreases withdistance from the optical axis.

Expanded Examples of Embodiments 1 to 6

Embodiments 1 to 6 have been described above as examples of thetechnology disclosed in the present application. However, the technologyin the present disclosure is not limited thereto, and is also applicableto embodiments in which changes, substitutions, additions, omissions,and/or the like are made as appropriate.

For example, the following materials may be adopted instead of thematerial of the cemented lenses exemplified in Embodiments 1 to 6. Thepurpose of adopting the following materials is to allow a relativerefractive index temperature coefficient in an atmosphere at 0 to 20° C.with respect to light having a wavelength range of 580 to 640 nm tosatisfy a predetermined condition described later. The materials of thecemented lenses are not limited to those described below, and anymaterial may be adopted as long as it is suited to the above purpose.

Alternatives of glass materials adoptable for the above-described lenselements having negative optical power are as follows:

a) HOYA Corporation

Glass name: M-FDS2, M-FDS1, M-FDS910,

-   -   M-FD80, M-NBFD10, M-TAFD307

b) Sumita Optical Glass Inc.

Glass name: K-PSFn203, K-PSFn2, K-PSFn5,

-   -   K-PSFn1, K-PSFn4, K-PSFn3,    -   K-VC91, K-VC90, K-ZnSF8, K-PG395,    -   K-CD45, K-CD 120

c) Ohara Corporation

Glass name: L-BBH1, L-BBH2, L-NBH54, L-TIH53,

-   -   L-LAH86, L-TIM28

Examples of glass materials adoptable for the above-described lenselements having positive optical power are as follows:

d) HOYA Corporation

Glass name: M-FCD500, M-BACD5N, M-PCD51,

-   -   M-BACD12, M-PCD4, M-BACD12,    -   M-BACD15, M-LAC14, M-LAC130,    -   M-LAC8, M-TAC80, M-TAC60

e) Sumita Optical Glass Inc.

Glass name: K-GFK70, K-GFK68, K-PSK300,

-   -   K-LaFK60, K-PSK11, K-CSK120,    -   K-PSK100, K-VC79, K-PSK200,    -   K-VC78, K-LaFK55, K-VC80,    -   K-LaFK50

f) Ohara Corporation

Glass name: L-LAL13, L-LAL12, L-BAL43,

-   -   L-BAL42, L-BAL35, S-FPM2,    -   L-PHL2

The following description is given for beneficial conditions that asingle focal length lens system like the single focal length lenssystems according to Embodiments 1 to 6 can satisfy. Here, a pluralityof beneficial conditions are set forth for the single focal length lenssystem according to each embodiment. A construction that satisfies allthe plurality of conditions is most effective for the single focallength lens system. However, when an individual condition is satisfied,a single focal length lens system having the corresponding effect can beobtained.

For example, like the single focal length lens systems according toEmbodiments 1 to 6, a single focal length lens system according to thepresent disclosure, in order from the object side to the image side,includes a first unit, an aperture diaphragm, and a second unit, inwhich the second unit includes a cemented lens having positive opticalpower, and a joint surface of the cemented lens is an aspheric surface.Hereinafter, this lens configuration is referred to as a basicconfiguration of the embodiments.

Since the joint surface of the cemented lens in the second unit is anaspheric surface, color aberration can be satisfactorily compensatedfor.

In the single focal length lens system having the basic configuration,the cemented lens in the second unit satisfies the following condition(1):

|dn/dt1|_(MAX)≦2.67×10⁻⁵  (1)

where

|dn/dt1|_(MAX) is a maximum value of absolute values of relativerefractive index temperature coefficients in an atmosphere at 0 to 20°C. with respect to light having a wavelength range of 580 to 640 nm,which is calculated for each lens element constituting the cementedlens.

The condition (1) is a condition regarding the relative refractive indextemperature coefficient of each lens element constituting the cementedlens in the second unit. When the condition (1) is satisfied, therelative refractive index temperature coefficient of the cemented lenshaving the positive optical power and the aspheric joint surface can bereduced. Therefore, it is possible to reduce defocusing in the opticalaxis direction which is caused by that the refractive index of the lenselement changes when the temperature changes.

When the following condition (1)′ is satisfied, the above effect can beachieved more successfully:

|dn/dt1|_(MAX)≦7.50×10⁻⁶  (1)′

Regarding the defocusing in the optical axis direction which is causedby that the refractive index of the lens element changes when thetemperature changes, it is beneficial to satisfy the following condition(a):

|dBF/f|≦3.50×10⁻⁴  (a)

where

dBF is defocusing in the optical axis direction which is caused by achange in the refractive index of each lens element per temperaturechange of 1° C., and

f is a focal length at d-line of the entire system.

In single focal length lens systems according to Numerical Examples 1 to6 described later, the above condition (a) is satisfied when thecemented lens in the second unit satisfies the above condition (1).

In the present disclosure, for simplification, exponent notation definedin JIS X 0210 “Representation of Numerical Values in Character Stringsfor Information Interchange” may be used. For example, “2.67×10⁻⁵” isexpressed as “2.67E-05”.

It is beneficial that a single focal length lens system having the basicconfiguration like the single focal length lens system according toEmbodiments 1 to 6 satisfies the following condition (2):

2ω_(DIA)≧150  (2)

where

2ω_(DIA) is a diagonal angle of view)(°).

The condition (2) is a condition regarding the diagonal angle of view ofthe single focal length lens system. In the single focal length lenssystem according to the present disclosure, defocusing in the opticalaxis direction, which is caused by that the refractive index of the lenselement changes when the temperature changes, can be reduced whilesatisfying the condition (2).

The single focal length lens system according to the present disclosurecan also achieve the above effect by satisfying the following condition(2)′:

2ω_(DIA)≧160  (2)′

The single focal length lens systems according to Numerical Examples 1to 6 described later realize a wider angle of view while maintainingexcellent optical performance by satisfying the condition (2).

When a camera equipped with the single focal length lens systemaccording to the present disclosure is installed in a position on therear side of the body of an automobile to be used as an in-vehiclecamera for checking a rear view, it is beneficial that the diagonalangle of view is large and that the horizontal angle of view is alsolarge to some extent.

For example, according to an advisory from National Highway TrafficSafety Administration in the USA, as shown in a schematic view of FIG.14, there are seven points A to G at which it is determined whethervisual recognition of a rear view behind a vehicle by an in-vehiclecamera is possible or not, and a range including the seven points A to Ghas a size of 3.04 m×6.10 m. That is, installation of an in-vehiclecamera capable of providing an image (video) with which a driver canvisually recognize an object, a person, or the like existing in therange of about 3 m×6 m on the rear side of the vehicle, is going to bemandatory in the USA.

In the case where an image (video) with which a driver can visuallyrecognize an object, a person, or the like having a height of about 80cm (as high as the average height of infants), for example, is providedat two points F and G closest to the vehicle among the seven points A toG, it is beneficial that the single focal length lens system mounted tothe in-vehicle camera satisfies the following condition (b):

2ω_(HOR)≧176  (b)

where

2ω_(HOR) is a horizontal angle of view)(°)

The horizontal angle of view of each of the single focal length lenssystems according to Numerical Examples 1 to 6 shown in Table 19 lateris a value calculated on the assumption that the ratio of the horizontalwidth to the vertical width of an imaging device included in the cameraaccording to the present disclosure is 4:3 (=horizontal width: verticalwidth). When it is assumed that the ratio is 16:9 (=horizontal width:vertical width), the horizontal angle of view of the single focal lengthlens system becomes wider.

It is beneficial that a single focal length lens system having the basicconfiguration like the single focal length lens system according toEmbodiments 1 to 6 satisfies the following condition (3):

2.0<f _(CEM) /f<4.0  (3)

where

f_(CEM) is a focal length at d-line of the cemented lens, and

f is the focal length at d-line of the entire system.

The condition (3) is a condition regarding the ratio of the focal lengthof the cemented lens in the second unit to the focal length of theentire single focal length lens system. When the condition (3) issatisfied, the optical power of the cemented lens in the single focallength lens system can be adjusted to an appropriate value, therebyrealizing a compact single focal length lens system having excellentaberration performance. When the value exceeds the upper limit of thecondition (3), the optical power of the cemented lens becomesexcessively small and the overall length of the lens system isincreased, which makes it difficult to reduce the size of the singlefocal length lens system. When the value goes below the lower limit ofthe condition (3), the optical power of the cemented lens becomesexcessively large and generated aberrations become large, which makesappropriate aberration compensation difficult.

When at least one of the following conditions (3)′ and (3)″ issatisfied, the above effect can be achieved more successfully:

2.4<f _(CEM) /f  (3)′

f _(CEM) /f<3.5  (3)″

The single focal length lens systems according to Numerical Examples 1to 6 described later achieve both further size reduction and maintenanceof excellent aberration performance by satisfying the condition (3).

In a single focal length lens system having the basic configuration likethe single focal length lens system according to Embodiments 1 to 6, itis beneficial that the first unit includes a lens element made of glassand located at a position closest to the object side. Thus, by locatingthe lens element made of glass at the position closest to the objectside in the entire system, environmental resistance of the single focallength lens system can be improved.

It is beneficial that a single focal length lens system having the basicconfiguration like the single focal length lens systems according toEmbodiments 1 to 6, in which the first unit, in order from the objectside to the image side, comprises a negative meniscus lens element withthe convex surface facing the object side, a lens element havingnegative optical power (hereinafter sometimes abbreviated as a negativelens element), and a lens element having positive optical power(hereinafter sometimes abbreviated as a positive lens element),satisfies the following condition (4):

|dn/dt2|_(MAX)≧9.00×10⁻⁵  (4)

where

|dn/dt2|_(MAX) is a maximum value of absolute values of relativerefractive index temperature coefficients in an atmosphere at 0 to 20°C. with respect to light having a wavelength range of 580 to 640 nm,which is calculated for the negative lens element and the positive lenselement constituting the first unit.

The condition (4) is a condition regarding the relative refractive indextemperature coefficient of the negative lens element and the positivelens element constituting the first unit. When the condition (4) issatisfied, the optical power of each lens element located on the objectside relative to the cemented lens in the second unit can be relativelyreduced. Therefore, even when the absolute value of the relativerefractive index temperature coefficient is large, defocusing in theoptical axis direction which is caused by that the refractive index ofthe lens element changes when the temperature changes can be canceled byappropriately combining the positive lens element and the negative lenselement. Further, when a lens element made of resin and having anaspheric surface is adopted as each of the positive lens element and thenegative lens element, cost reduction can be achieved whilesatisfactorily compensating for various aberrations.

When the following condition (4)′ is satisfied, the above effect can beachieved more successfully:

|dn/dt2|mAx≧1.00×10⁻⁴  (4)′

The single focal length lens systems according to Numerical Examples 1,4 and 5 described later satisfy the condition (4). Therefore, the singlefocal length lens systems according to Numerical Example 1, 4 and 5 areconfigured so as to satisfy the above condition (a) even if thecondition (4) is satisfied.

It is beneficial that a single focal length lens system having the basicconfiguration like the single focal length lens systems according toEmbodiments 1 to 6, in which the cemented lens is composed of a negativelens element and a positive lens element, satisfies the followingcondition (5):

Nd _(MIN)>1.50  (5)

where

Nd_(MIN) is a refractive index at d-line of the positive lens elementconstituting the cemented lens.

The condition (5) is a condition regarding the refractive index of thepositive lens element constituting the cemented lens. When the condition(5) is satisfied, the curvature radius of the cemented lens can beincreased. As a result, the inclination angle of a peripheral portion ofthe cemented lens can be made gentle, whereby the level of difficulty inmanufacturing the cemented lens can be reduced to achieve costreduction.

When the following condition (5)′ is satisfied, the above effect can beachieved more successfully:

Nd _(MIN)>1.55  (5)′

The single focal length lens systems according to Numerical Examples 1to 6 described later realize further cost reduction by satisfying thecondition (5).

Embodiment 7 Camera and Automobile

As an example of a camera equipped with the single focal length lenssystem according to Embodiment 1, an in-vehicle camera will bedescribed. In the in-vehicle camera, any one of the single focal lengthlens systems according to Embodiments 2 to 6 may be applied instead ofthe single focal length lens system according to Embodiment 1.

FIG. 13(a) is a schematic diagram showing an in-vehicle camera equippedwith the single focal length lens system according to Embodiment 1. Thein-vehicle camera 100 includes the single focal length lens system 201,and an imaging device 202 which captures an image of light converged bythe single focal length lens system 201.

The in-vehicle camera 100 is mounted on a vehicle, and is used as asensing camera or a view camera. An image captured by the sensing camerais used for checking a distance between the vehicle and another vehicle.An image captured by the view camera is displayed on a monitor installedin the vehicle, and is used by a driver to check the views in front ofand behind the vehicle.

The single focal length lens system according to the present disclosureis a lens system in which the temperature characteristics areconsidered, and significant widening of the diagonal angle of view to150° or more is achieved. Therefore, the single focal length lens systemcan suppress occurrence of aberrations in the captured image due totemperature change as much as possible, and is effective as a lenssystem for the view camera.

Next, as an example of an automobile according to the presentdisclosure, an automobile equipped with the above view camera will bedescribed.

FIG. 13(b) is a schematic diagram showing an automobile having thecamera at a position on the rear side thereof. The automobile has thein-vehicle camera 100 at a position on the rear side thereof, andincludes a processing unit (CPU) 300 which detects the externalenvironment on the basis of the image captured by the imaging device 202included in the in-vehicle camera 100, and controls each part.

The imaging device 202 receives the optical image formed by the singlefocal length lens system 201, and converts the optical image into anelectric image signal. The CPU 300 acquires the image signal, checkspresence of a pedestrian, an obstacle, or the like, and notifies thedriver of presence of a pedestrian, an obstacle, or the like on thebasis of the check result.

As described above, the single focal length lens system according to thepresent disclosure is effective as a lens system for the view camera,but can be used as a lens system for a sensing camera.

As described above, when the in-vehicle camera is applied as a rear viewcamera (in-vehicle camera for checking a rear view) among view cameras,it is beneficial that the diagonal angle of view is large and that thehorizontal angle of view is also large to some extent.

In the case where an image (video) which allows the driver to visuallyrecognize an object, a person, or the like having a height of about 80cm, for example, is provided at two points F and G closest to thevehicle among the seven points A to G at which it is determined whethervisual recognition of the rear view behind the vehicle by the rear viewcamera is possible or not, in the schematic diagram shown in FIG. 14, itis beneficial that the single focal length lens system included in thein-vehicle camera satisfies the above condition (b), i.e., that thehorizontal angle of view is 176° or more. Among the single focal lengthlens systems according to the present disclosure, the single focallength lens systems according to Embodiments 1 to 3 and 6 each have alarge horizontal angle of view of about 190°. Therefore, each of thesesingle focal length lens systems allows visual recognition of a widerview behind the vehicle, and is very effective as a lens system for therear view camera.

Embodiment 7 has been described as an example of the technologydisclosed in the present application. However, the technology in thepresent disclosure is not limited thereto, and is also applicable toembodiments in which changes, substitutions, additions, omissions,and/or the like are made as appropriate.

While an example in which the single focal length lens system accordingto any of Embodiments 1 to 6 of the present disclosure is applied to thein-vehicle camera which is the sensing camera or the view camera hasbeen described as Embodiment 7, the single focal length lens systemaccording to the present disclosure is also applicable to, for example,a monitor camera in a monitor system, a Web camera, and the like.

Numerical Examples 1 to 6

The following description is given for numerical examples in which thesingle focal length lens systems according to Embodiments 1 to 6 areimplemented practically. In each numerical example, the units of thelength in the tables are all “mm”, and the units of the view angle areall “°”. In the tables, “view angle” means a diagonal half angle ofview. In each numerical example, r is the radius of curvature, d is theaxial distance, nd is the refractive index to the d-line, vd is the Abbenumber to the d-line, and dn/dt is a relative refractive indextemperature coefficient in an atmosphere at 0 to 20° C. with respect tolight having a wavelength range of 580 to 640 nm. In each numericalexample, the surfaces marked with * are aspheric surfaces, and theaspheric surface configuration is defined by the following expression:

$Z = {\frac{h^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right)\left( {h/r} \right)^{2}}}} + {\sum{A_{n}h^{n}}}}$

where

Z is the distance from a point on an aspherical surface at a height hrelative to the optical axis to a tangential plane at the vertex of theaspherical surface,

h is the height relative to the optical axis,

r is the radius of curvature at the top,

κ is the conic constant, and

A_(n) is the n-th order aspherical coefficient.

FIGS. 2, 4, 6, 8, 10 and 12 are longitudinal aberration diagrams, in theinfinity in-focus condition, of the single focal length lens systemsaccording to Numerical Examples 1 to 6, respectively.

Each longitudinal aberration diagram, in order from the upper side,shows the spherical aberration (SA (mm)), the astigmatism (AST (mm)),and the distortion (DIS (%)).

In each spherical aberration diagram, the vertical axis indicates theF-number (in each Fig., indicated as F), and the solid line, the shortdash line, and the long dash line indicate the characteristics to thed-line, the F-line, and the C-line, respectively.

In each astigmatism diagram, the vertical axis indicates the imageheight, and w indicates the diagonal half angle of view. The solid lineand the dash line indicate the characteristics to the sagittal plane (ineach Fig., indicated as “s”) and the meridional plane (in each Fig.,indicated as “m”), respectively.

In each distortion diagram, the vertical axis indicates the imageheight, and w indicates the diagonal half angle of view. The solid lineindicates the distortion when Y 2×f×tan(ω/2) (Y: the image height, f:the focal length of the entire system) is an ideal image height(stereographic projection method).

Numerical Example 1

The single focal length lens system of Numerical Example 1 correspondsto Embodiment 1 shown in FIG. 1. Table 1, Table 2, and Table 3 show thesurface data, the aspherical data, and the various data, respectively,of the single focal length lens system of Numerical Example 1.

TABLE 1 (Surface data) Surface number r d nd vd dn/dt Object surface ∞ 1 11.35070 0.60000 1.83481 42.7 4.70E−06  2 3.70350 2.32000  3*−33.90210 0.60000 1.53460 56.3 −9.20E−05  4* 1.40460 1.33000  5*18.02970 1.50000 1.63450 23.9 −1.10E−04  6* −3.47580 0.96500  7(Diaphragm) ∞ 0.60000  8* 2.41960 0.60000 1.83271 24.1 −1.10E−06  9*1.06890 1.71000 1.61881 63.9 −2.90E−06 10* −2.28030 1.67420 11 ∞ 0.700001.51680 64.1 2.20E−06 12 ∞ 0.10000 13 ∞ (BF) Image surface ∞

TABLE 2 (Aspherical data) Surface No. 3 K = −3.17199E+02, A4 =1.09422E−03, A6 = −1.21083E−04, A8 = −1.61127E−05 A10 = 1.45427E−06, A12= 0.00000E+00, A14 = 0.00000E+00, A16 = 0.00000E+00 Surface No. 4 K =−5.80806E−01, A4 = 1.41103E−02, A6 = −1.86620E−03, A8 = 7.07398E−03 A10= −1.71716E−03, A12 = −4.33448E−04, A14 = 5.02234E−04, A16 =−1.00984E−04 Surface No. 5 K = 8.20985E+01, A4 = 4.08397E−03, A6 =3.87174E−03, A8 = −4.22244E−04 A10 = 0.00000E+00, A12 = 0.00000E+00, A14= 0.00000E+00, A16 = 0.00000E+00 Surface No. 6 K = −2.13843E+00, A4 =6.46864E−03, A6 = −2.56893E−03, A8 = −2.17942E−04 A10 = 0.00000E+00, A12= 0.00000E+00, A14 = 0.00000E+00, A16 = 0.00000E+00 Surface No. 8 K =3.98312E−01, A4 = −8.81298E−03, A6 = 7.79660E−04, A8 = −2.62717E−03 A10= 2.00824E−03, A12 = −8.08704E−04, A14 = −2.00864E−06, A16 =−1.32875E−06 Surface No. 9 K = −6.78769E−01, A4 = 6.81879E−02, A6 =−8.10911E−02, A8 = 2.89796E−02 A10 = 3.42269E−03, A12 = −2.31368E−03,A14 = −2.71488E−03, A16 = 5.80436E−04 Surface No. 10 K = −1.11291E+00,A4 = 8.63634E−03, A6 = −4.63511E−03, A8 = 2.27847E−02 A10 =−1.51526E−02, A12 = −9.53189E−04, A14 = 5.62029E−03, A16 = −1.57910E−03

TABLE 3 (Various data) Focal length 0.9801 F-number 2.07010 View angle108.0000 Image height 1.9000 Overall length of lens 12.6841 BF −0.01512Entrance pupil position 3.0287 Exit pupil position −6.3628 Frontprincipal point position 3.8574 Rear principal point position 11.7040Single lens data Lens Initial surface No. Focal length 1 1 −6.8286 2 3−2.5080 3 5 4.7204 4 8 −2.8809 5 9 1.4613 Cemented lens data Initialsurface No. Final surface No. Focal length 8 10 2.7807

Numerical Example 2

The single focal length lens system of Numerical Example 2 correspondsto Embodiment 2 shown in FIG. 3. Table 4, Table 5, and Table 6 show thesurface data, the aspherical data, and the various data, respectively,of the single focal length lens system of Numerical Example 2.

TABLE 4 (Surface data) Surface number r d nd vd dn/dt Object surface ∞ 1 8.69940 0.60000 1.83481 42.7 4.70E−06  2 3.05460 2.45290  3 −22.678700.72110 1.77250 49.6 4.80E−06  4 1.89430 0.77250  5 188.81560 2.814501.90366 31.3 3.40E−06  6 −4.15070 0.19470  7 (Diaphragm) ∞ 0.75700  8*2.77870 3.06110 1.72903 54.0 4.10E−06  9* −1.22220 0.50000 2.00178 19.36.30E−06 10* −3.14200 1.37180 11 ∞ 0.70000 1.51680 64.1 2.20E−06 12 ∞0.10000 13 ∞ (BF) Image surface ∞

TABLE 5 (Aspherical data) Surface No. 8 K = 3.70812E−02, A4 =3.34078E−03, A6 = 2.96074E−03, A8 = −8.63765E−04 Surface No. 9 K =−8.91526E−01, A4 = −3.30865E−02, A6 = 8.86206E−03, A8 = 5.10167E−03Surface No. 10 K = −1.35766E+01, A4 = −2.49491E−02, A6 = 1.95944E−02, A8= −3.20199E−04

TABLE 6 (Various data) Focal length 1.0458 F-number 2.05929 View angle107.0000 Image height 14.0738 Overall length of lens 12.6841 BF 0.02818Entrance pupil position 2.8513 Exit pupil position −7.0220 Frontprincipal point position 3.7419 Rear principal point position 13.0280Single lens data Lens Initial surface No. Focal length 1 1 −5.9256 2 3−2.2346 3 5 4.5258 4 8 1.7188 5 9 −2.2960 Cemented lens data Initialsurface No. Final surface No. Focal length 8 10 3.3089

Numerical Example 3

The single focal length lens system of Numerical Example 3 correspondsto Embodiment 3 shown in FIG. 5. Table 7, Table 8, and Table 9 show thesurface data, the aspherical data, and the various data, respectively,of the single focal length lens system of Numerical Example 3.

TABLE 7 (Surface data) Surface number r d nd vd dn/dt Object surface ∞ 1 7.87980 0.60000 1.83481 42.7 4.70E−06  2 3.17420 1.69190  3 22.036300.60000 1.77250 49.6 4.80E−06  4 1.60000 1.71810  5 71.26080 2.079501.90366 31.3 3.40E−06  6 −3.44130 0.16080  7 (Diaphragm) ∞ 0.92020  8*2.89540 0.94730 1.82115 24.1 −2.00E−07  9* 0.85900 2.10720 1.61881 63.9−2.90E−06 10* −2.10700 1.32820 11 ∞ 0.70000 1.51680 64.1 2.20E−06 12 ∞0.10000 13 ∞ (BF) Image surface ∞

TABLE 8 (Aspherical data) Surface No. 8 K = −8.88056E−01, A4 =−8.21796E−03, A6 = −4.02136E−03, A8 = 2.92067E−03 A10 = −6.35903E−04,A12 = 0.00000E+00 Surface No. 9 K = −1.07923E+00, A4 = 5.38597E−02, A6 =−5.47753E−02, A8 = 1.84038E−02 A10 = −1.16473E−03, A12 = −8.46024E−04Surface No. 10 K = −7.62804E−01, A4 = 2.28416E−03, A6 = 1.26424E−02, A8= −7.95749E−03 A10 = 2.46051E−03, A12 = 0.00000E+00

TABLE 9 (Various data) Focal length 0.9964 F-number 2.07826 View angle109.0000 Image height 1.9559 Overall length of lens 12.9880 BF 0.03478Entrance pupil position 2.7122 Exit pupil position −12.0223 Frontprincipal point position 3.6263 Rear principal point position 11.9916Single lens data Lens Initial surface No. Focal length 1 1 −6.7593 2 3−2.2623 3 5 3.6814 4 8 −1.8821 5 9 1.3538 Cemented lens data Initialsurface No. Final surface No. Focal length 8 10 3.3167

Numerical Example 4

The single focal length lens system of Numerical Example 4 correspondsto Embodiment 4 shown in FIG. 7. Table 10, Table 11, and Table 12 showthe surface data, the aspherical data, and the various data,respectively, of the single focal length lens system of NumericalExample 4.

TABLE 10 (Surface data) Surface number r d nd vd dn/dt Object surface ∞ 1 37.92220 0.60000 1.72916 54.7 2.60E−06  2 6.70500 2.70000  3*−835.48100 0.84000 1.53460 56.3 −9.20E−05  4* 2.66920 2.81000  5*11.09970 3.09000 1.63450 23.9 −1.10E−04  6* −8.83650 0.45000  7(Diaphragm) ∞ 0.06000  8* 4.68880 2.15550 1.68893 31.2 −2.90E−06  9*1.16450 2.90750 1.55332 71.7 −5.70E−06 10* −3.95110 4.21560 11 ∞ 0.900001.51680 64.2 2.60E−06 12 ∞ 0.30000 13 ∞ (BF) Image surface ∞

TABLE 11 (Aspherical data) Surface No. 3 K = 1.00000E+03, A4 =4.07645E−04, A6 = −3.78260E−07, A8 = −9.85094E−08 A10 = −1.33542E−08,A12 = −8.45609E−10, A14 = −7.49711E−12, A16 = −6.25430E−13 Surface No. 4K = −8.25858E−01, A4 = 2.57983E−05, A6 = 2.23395E−04, A8 = 5.79271E−06A10 = 3.72598E−06, A12 = 7.21702E−09, A14 = 0.00000E+00, A16 =0.00000E+00 Surface No. 5 K = −3.39245E+01, A4 = 1.38898E−03, A6 =1.24680E−04, A8 = −1.56215E−06 A10 = 4.29395E−06, A12 = 2.45888E−07, A14= 0.00000E+00, A16 = 0.00000E+00 Surface No. 6 K = 1.10394E+00, A4 =−8.14425E−04, A6 = 9.44115E−04, A8 = −3.93687E−05 A10 = 2.93378E−06, A12= 5.03951E−08, A14 = −3.34428E−07, A16 = 5.75048E−07 Surface No. 8 K =−2.57270E+00, A4 = −9.82327E−04, A6 = 7.72242E−04, A8 = 1.89571E−04 A10= −2.55084E−04, A12 = 1.39069E−04, A14 = 6.11709E−05, A16 = −4.97849E−05Surface No. 9 K = −9.39432E−01, A4 = −7.58456E−03, A6 = 2.94691E−04, A8= 9.79729E−04 A10 = −8.26440E−06, A12 = −3.64238E−05, A14 = 2.64487E−05,A16 = −8.11723E−06 Surface No. 10 K = −1.90909E+00, A4 = −1.11112E−03,A6 = 5.28479E−04, A8 = −1.26240E−04 A10 = −9.92121E−06, A12 =2.82318E−06, A14 = 8.43271E−07, A16 = −3.14709E−07

TABLE 12 (Various data) Focal length 2.5577 F-number 2.90243 View angle80.0000 Image height 3.5931 Overall length of lens 21.0449 BF 0.01630Entrance pupil position 4.2490 Exit pupil position −10.3679 Frontprincipal point position 6.1767 Rear principal point position 18.4872Single lens data Lens Initial surface No. Focal length 1 1 −11.2618 2 3−4.9753 3 5 8.2502 4 8 −2.9963 5 9 2.0381 Cemented lens data Initialsurface No. Final surface No. Focal length 8 10 6.5624

Numerical Example 5

The single focal length lens system of Numerical Example 5 correspondsto Embodiment 5 shown in FIG. 9. Table 13, Table 14, and Table 15 showthe surface data, the aspherical data, and the various data,respectively, of the single focal length lens system of NumericalExample 5.

TABLE 13 (Surface data) Surface number r d nd vd dn/dt Object surface ∞ 1 38.72870 0.60000 1.72916 54.7 2.60E−06  2 6.63090 2.30000  3*−229.63260 0.84000 1.53460 56.3 −9.20E−05  4* 2.68390 2.85000  5*10.93090 3.09000 1.63450 23.9 −1.10E−04  6* −8.71100 0.47000  7(Diaphragm) ∞ 0.00000  8* 5.81610 2.40000 1.82115 24.1 −2.00E−07  9*1.64400 2.95000 1.61881 63.9 −2.90E−06 10* −4.15220 4.35500 11 ∞ 0.900001.51680 64.2 2.60E−06 12 ∞ 0.30000 13 ∞ (BF) Image surface ∞

TABLE 14 (Aspherical data) Surface No. 3 K = 1.00000E+03, A4 =4.07630E−04, A6 = −4.09635E−07, A8 = −1.02624E−07 A10 = −1.36542E−08,A12 = −8.51123E−10, A14 = −6.47434E−12, A16 = −4.26061E−13 Surface No. 4K = −8.26237E−01, A4 = 2.25543E−05, A6 = 2.23243E−04, A8 = 5.83952E−06A10 = 3.73936E−06, A12 = 9.83906E−09, A14 = 0.00000E+00, A16 =0.00000E+00 Surface No. 5 K = −3.38965E+01, A4 = 1.39142E−03, A6 =1.25248E−04, A8 = −1.38836E−06 A10 = 4.35285E−06, A12 = 2.65445E−07, A14= 0.00000E+00, A16 = 0.00000E+00 Surface No. 6 K = 1.07958E+00, A4 =−8.10132E−04, A6 = 9.49817E−04, A8 = −3.72019E−05 A10 = 3.00728E−06, A12= −5.99960E−07, A14 = −7.14312E−07, A16 = 3.29022E−07 Surface No. 8 K =−6.22451E−01, A4 = −2.20975E−03, A6 = −1.71634E−05, A8 = 8.30452E−04 A10= −2.37223E−04, A12 = −8.76248E−05, A14 = 1.00417E−05, A16 = 1.81446E−05Surface No. 9 K = −8.91638E−01, A4 = −8.12343E−03, A6 = −5.92764E−04, A8= 8.23238E−04 A10 = −1.63472E−04, A12 = 9.70445E−06, A14 = 6.34900E−06,A16 = −1.16995E−06 Surface No. 10 K = −2.11980E+00, A4 = −6.16754E−04,A6 = 4.65339E−04, A8 = −5.80184E−05 A10 = 3.77877E−06, A12 =−2.44485E−07, A14 = 5.38180E−07, A16 = −9.44250E−08

TABLE 15 (Various data) Focal length 2.5944 F-number 2.89890 View angle80.0000 Image height 3.5924 Overall length of lens 21.0665 BF 0.01154Entrance pupil position 4.0506 Exit pupil position −10.5328 Frontprincipal point position 6.0066 Rear principal point position 18.4722Single lens data Lens Initial surface No. Focal length 1 1 −11.0597 2 3−4.9561 3 5 8.1372 4 8 −3.7684 5 9 2.3629 Cemented lens data Initialsurface No. Final surface No. Focal length 8 10 6.6150

Numerical Example 6

The single focal length lens system of Numerical Example 6 correspondsto Embodiment 6 shown in FIG. 11. Table 16, Table 17, and Table 18 showthe surface data, the aspherical data, and the various data,respectively, of the single focal length lens system of NumericalExample 6.

TABLE 16 (Surface data) Surface number r d nd vd dn/dt Object surface ∞ 1 9.00620 0.60000 1.83481 42.7 4.70E−06  2 3.00700 2.40280  3 −27.069200.73760 1.77250 49.6 4.80E−06  4 1.89060 0.77430  5 141.82810 2.820501.90366 31.3 3.40E−06  6 −4.16160 0.20770  7 (Diaphragm) ∞ 0.78630  8*2.70060 3.05190 1.72903 54.0 4.10E−06  9* −1.36960 0.50000 2.14780 17.32.67E−05 10* −2.99990 1.36780 11 ∞ 0.70000 1.51680 64.1 2.20E−06 12 ∞0.10000 13 ∞ (BF) Image surface ∞

TABLE 17 (Aspherical data) Surface No. 8 K = −9.59574E−02, A4 =3.40436E−03, A6 = 2.98797E−03, A8 = −6.90765E−04 Surface No. 9 K =−1.00383E+00, A4 = −2.77855E−02, A6 = 4.22185E−04, A8 = 6.41574E−03Surface No. 10 K = −1.14849E+01, A4 = −2.72463E−02, A6 = 1.80108E−02, A8= 1.82867E−04

TABLE 18 (Various data) Focal length 1.0424 F-number 2.07151 View angle107.0000 Image height 1.9453 Overall length of lens 14.0835 BF 0.03458Entrance pupil position 2.7915 Exit pupil position −7.0516 Frontprincipal point position 3.6806 Rear principal point position 13.0411Single lens data Lens Initial surface No. Focal length 1 1 −5.6653 2 3−2.2625 3 5 4.5154 4 8 1.8228 5 9 −2.6261 Cemented lens data Initialsurface No. Final surface No. Focal length 8 10 3.3289

The following Table 19 shows the corresponding values to the individualconditions in the single focal length lens systems according to therespective Numerical Examples.

TABLE 19 (Values corresponding to conditions) Numerical ExamplesConditions 1 2 3 4 5 6 (1) |dn/dt1|_(MAX) 2.90E−06 6.30E−06 2.90E−065.70E−06 2.90E−06 2.67E−05 (2) 2ω_(DIA) 216 214 218 160 160 214 (3)f_(CEM)/f 2.8372 3.1641 3.3286 2.5657 2.5498 3.1935 (4) |dn/dt2|_(MAX)1.10E−04 4.80E−06 4.80E−06 1.10E−04 1.10E−04 4.80E−06 (5) Nd_(MIN)1.61881 1.72903 1.61881 1.55332 1.61881 1.72903 (a) |dBF/f| 1.59E−041.46E−05 2.11E−05 2.50E−04 2.29E−04 1.68E−05 (b) 2ω_(HOR) 193 189 193124 123 190 f 0.9801 1.0458 0.9964 2.5577 2.5944 1.0424 f_(CEM) 2.78073.3089 3.3167 6.5624 6.6150 3.3289 dBF 1.56E−04 −1.52E−05 2.10E−056.40E−04 5.95E−04 1.75E−05

The present disclosure is applicable to an in-vehicle camera, a monitorcamera, a Web camera, and the like. In particular, the presentdisclosure is beneficial in a camera which is required to have awide-angle lens system, such as an in-vehicle camera and a monitorcamera.

As presented above, the embodiments have been described as examples ofthe technology according to the present disclosure. For this purpose,the accompanying drawings and the detailed description are provided.

Therefore, components in the accompanying drawings and the detaildescription may include not only components essential for solvingproblems, but also components that are provided to illustrate the abovedescribed technology and are not essential for solving problems.Therefore, such inessential components should not be readily construedas being essential based on the fact that such inessential componentsare shown in the accompanying drawings or mentioned in the detaileddescription.

Further, the above described embodiments have been described toexemplify the technology according to the present disclosure, andtherefore, various modifications, replacements, additions, and omissionsmay be made within the scope of the claims and the scope of theequivalents thereof.

What is claimed is:
 1. A single focal length lens system, in order froman object side to an image side, comprising: a first unit; an aperturediaphragm; and a second unit, wherein the first unit includes a lenselement made of glass at a position closest to the object side, thesecond unit includes a cemented lens having positive optical power, anda joint surface of the cemented lens is an aspheric surface, and thefollowing conditions (1), (2) and (3) are satisfied:|dn/dt1|_(MAX)≦2.67×10⁻⁵  (1)2ω_(DIA)≧150  (2)2.0<f _(CEM) /f<4.0  (3) where |dn/dt1|_(MAX) is a maximum value ofabsolute values of relative refractive index temperature coefficients inan atmosphere at 0 to 20° C. with respect to light having a wavelengthrange of 580 to 640 nm, which is calculated for each of lens elementsconstituting the cemented lens, 2ω_(DIA) is a diagonal angle ofview)(°), f_(CEM) is a focal length at d-line of the cemented lens, andf is a focal length at d-line of the entire system.
 2. The single focallength lens system as claimed in claim 1, wherein the first unit, inorder from the object side to the image side, comprises: the lenselement that is disposed at the position closest to the object side andthat is a negative meniscus lens element with a convex surface facingthe object side; a lens element having negative optical power, and alens element having a positive optical power, and the followingcondition (4) is satisfied:|dn/dt2|_(MAX)≧9.00×10⁻⁵  (4) where |dn/dt2|_(MAX) is a maximum value ofabsolute values of relative refractive index temperature coefficients inan atmosphere at 0 to 20° C. with respect to light having a wavelengthrange of 580 to 640 nm, which is calculated for each of the lens elementhaving negative optical power and the lens element having positiveoptical power, which constitute the first unit.
 3. The single focallength lens system as claimed in claim 1, wherein the cemented lenscomprises a lens element having negative optical power and a lenselement having positive optical power, and the following condition (5)is satisfied:Nd _(MIN)>1.50  (5) where Nd_(MIN) is a refractive index at d-line ofthe lens element having positive optical power, which constitute thecemented lens.
 4. A camera comprising: the single focal length lenssystem as claimed in claim 1; and an imaging device which captures animage of light converged by the single focal length lens system.
 5. Anautomobile comprising: the camera as claimed in claim 4; and aprocessing unit which detects external environment on the basis of theimage captured by the imaging device included in the camera, andcontrols each part.